For the early diagnosis of lung cancer, typically small biopsies are taken from the lung. Such biopsies can be obtained for instance through percutaneous insertions of a biopsy needle, or by introducing a bronchoscope into the airways of the lung (bronchi) with a biopsy tool via the working channel. For the latter, several types of biopsy tools can be used to obtain different kinds of tissue samples, such as forceps biopsies, needle aspiration biopsies, and brush biopsies for cytology. The sample should be of sufficient size to provide the pathologist with ample material for a proper evaluation.
Typical bronchoscopes are equipped with visual confirmation tools, allowing for inspection of the tissue sample prior to taking the biopsy. However, the size of such bronchoscopes with integrated optics does not allow for probing tissue from remote regions within the lung (small bronchi) with visual confirmation Such regions may be reached by protruding a smaller, flexible biopsy tool through the working channel of the bronchoscope, but the visual confirmation is not available any more. Further, the visual inspection can only confirm the presence of lesions which are visible on the surface of the bronchi. For the detection of tumors at an early stage, which typically originate behind the bronchi wall, the visual inspection is limited by the intrinsically superficial information. Further, the dimensions of the flexible tool will determine how deep the tool can be inserted into the bronchi, and should be therefore as compact as possible. For very small bronchi, it becomes important that the tool is capable of side-looking: Lesions behind the bronchi wall cannot be detected if the detection method is only forward directed, since there is no room left for positioning the front of the tool tip towards the suspected lesion.
As a result, potentially malignant lesions are often not noticed and/or the biopsy is taken at the wrong location resulting in false negatives. The number of biopsies should also be kept to a minimum, since every biopsy obtained has a risk of causing internal bleeding in the lung.
A way to add tissue sensing is by adding optical fibers to the flexible biopsy tools. An example is described in patent application EP 0910284 B1 where a forceps tool with in the center a fiber is integrated for tissue sensing based on optical spectroscopy. Studies have shown that lung tumors can be discriminated from normal lung parenchyma based on scattering and water content in the tissue. To determine these tissue parameters the fiber ends of the sending and receiving fiber should be sufficiently apart to reliably determine these parameters. Furthermore, to determine these parameters the probe must be able to sense the lung parenchyma beyond the bronchi wall. This means that the fiber ends must be at least 0.5 mm apart, more preferably 1 mm apart.
Other ways of adding optical fibers to a biopsy tool are disclosed in patent applications WO 2014/132110A1, WO 00/42906 A2 and WO 2014/068468 A1.